Corrosion of metals is the destructive attack on the metal by the environment, by chemical, or by electrochemical processes with the most common kind of corrosion being that due to the reaction of atmospheric components such as oxygen with the metal. Rusting is an example of such corrosion.
In addition to oxygen, there are many pollutants in the atmosphere, such as ozone, nitrogen oxides, nitric acid, sulfur dioxide, sulfuric acid, carbonic acid, hydrochloric acid, tar acids and the like, which act to dissolve the metal surfaces and to pit the same.
Generally, the greater the relative humidity the greater the degree of corrosion. Metals subjected to immersion in water, such as seawater, rapidly corrode.
Efforts to prevent such corrosion include painting, plating, or otherwise coating the metal with corrosion-inhibiting materials such as the conventional chromate and zinc compounds used for that purpose. However, for many metal surfaces painting or other form of permanent or semi-permanent coating is not possible. Such is the case with the inner surfaces of internal combustion engines, for example. In such instances, it is common to use lubricating oils which contain conventional oxidation and rust inhibitors to prevent corrosion. While generally satisfactory for engines, such as automotive or aviation engines, which are in use on a regular basis; i.e., daily or at least several times a month, such inhibitors are generally ineffective for protecting the interior surfaces of such engines if the engines stand idle for long periods of time.
This lack of use is typical of agricultural equipment, lawn mowers, leaf blowers, snowthrowers, snowmobiles, outboard engines, stockpiled replacement engines, and many military vehicles which are stored for long periods of time without use. Despite the use of conventional preservative oils containing known corrosion inhibitors, the internal metal surfaces of such engines corrode and can become so damaged as to become unusable. This is due to the fact the preservative materials will either evaporate or drain off, particularly from vertical surfaces.
Efforts to overcome such corrosion problems include a regular maintenance schedule of starting and running the engines in an effort to keep the internal engine surface coated with preservatives. Such procedure is not only costly, but in many cases not possible. This is true in military depots and car manufacturing facilities where such a large number of vehicles and/or engines remain idled for a long period of time. In addition, such sporadic running of the engines cannot always assure that the metal surfaces will be coated sufficiently with preservatives to prevent corrosion damage.
The ineffectiveness of present preservative fluids is also true with respect to the other types of metal surfaces to which they are applied.